Twenty percent of adolescents will have at least one episode of clinical depression by age 18, and 65% will experience transient or less severe depressive symptoms. Depression compromises the process of adolescent development by interfering with academic, occupational, and social functioning, and increasing risk for substance use and suicide. Although Initial research provides some support for both pharmacological and psychosocial interventions for depressed youth, many teens do not respond to these interventions, and others experience a relapse of symptoms within one year. Furthermore, recent concerns about antidepressant medications increasing suicide risk have raised additional concerns about use of pharmacotherapy with adolescents. As such, the importance of developing innovative treatment options for depressed adolescents is critical. Cognitive Behavioral Therapy (CBT) has been demonstrated to be effective in the treatment of depressed adults, with more modest efficacy data when used with children and adolescents. Interestingly, recent data from the adult literature suggests the positive outcomes of CBT can be achieved and surpassed by interventions that are purely behavioral in nature. As behavioral interventions may be easier to implement with many adolescents innovative treatments with such a focus may provide a better developmental fit for depressed adolescents. The present project proposes to develop a manualized Behavioral Activation (BA) Therapy for depressed adolescents, test its adaptability, acceptability, and feasibility in an open clinical trial with 12 adolescents (aged 12-17), and following further treatment refinement, test its efficacy in a randomized controlled trial of 50 adolescents (aged 12-17), in which 25 will be randomized to BA Therapy and 25 will receive "Treatment as Usual (TAU)." In this randomized controlled trial, depressed adolescents will receive 12-weeks of BA Therapy or TAU. Psychiatric and psychosocial functioning will be assessed at the beginning, middle, and end of treatment. A naturalistic follow-up will be conducted 4 and 9 months post-treatment. Assuming that BA will outperform "usual" approaches to therapy with depressed youth, the data will provide the basis for the development of a larger randomized controlled trial comparing the efficacy of BA against other widely studied approaches to the treatment of depression in youth, namely pharmacotherapy in the form of Selective Serotonin Reuptake Inhibitors (SSRIs), and CBT. [unreadable] [unreadable] [unreadable]